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Energy from sources other than fossil and nuclear fuels is to a large extent free of the concerns about environmental effects and renewability that characterize those two sources. Each alternative source supplies energy continuall, whether or not we use it, and most have their origins in energy generated outside the Earth, yet the potential of each is limited by its total supply set against its rate of use. The Sun will radiate energy until it ceases thermonuclear fusion, in around 5 billion years. This free course, Energy resources: Solar energy, explores the Sun as a potential source of usable energy.
By the end of this free course you should be able to:
- explain the principles that underlie the ability of various natural phenomena to deliver solar energy;
- outline the technologies that are used to harness the power of solar energy;
- discuss the positive and negative aspects of solar energy in relation to natural and human aspects of the environment.
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Energy resources: Solar energy
Energy from sources other than fossil or nuclear fuels is to a large extent free of the concerns about environmental effects and renewability that characterise those two sources. Each alternative source supplies energy continually, whether or not we use it. Many alternative sources of energy have been used in simple ways for millennia, e.g. wind and water mills, sails, wood burning – but only in the last two centuries has their potential begun to be exploited on an industrial scale. Except for geothermal energy, all have their origins in energy generated outside the Earth, yet the potential of each is limited by its total supply set against its rate of use. Each is likely to be renewable in the sense that the available rates of supply of each exceed those at which they are used. The main concern is whether or not such alternatives can supplant fossil- and nuclear-fuel use to power social needs fast enough to avoid the likelihood of future global warming and other kinds of pollution.
One of the alternative sources to consider is solar energy.
The Sun will radiate energy until it ceases thermonuclear fusion, in around 5 billing years. About 33% of the solar power that enters the Earth's system heats the atmosphere and contributes to setting winds and waves in motion. Of that reaching the Earth's surface, 70% falls on the sea, setting in motion ocean currents and a large proportion of the circulation of water vapour in the atmosphere because of evaporation from the ocean surface. The remainder falls on the land. Solar energy is redistributed through interlinked surface systems:
- the carbon cycle based on photosynthesis;
- atmospheric circulation and the water cycle;
- winds and ocean waves; and the ocean current system.
Each of them is a potential source of useable energy. In every case, with the exception of the energy available from surface water flow, humanity comes nowhere near exploiting the Sun's potential to supply useable energy; in fact, we really do not know the practical limits. Whatever those are, they will not disappear as a resource – all are renewable. Compare this with the solar energy stored chemically by the degraded products of photosynthesis in fossil fuels. Although carbon burial adds continually to that resource, its pace of renewal (between 1 to 10 GW – Figure 1) is about 2000 times slower than we use it. Fossil fuels are non-renewable and declining extremely quickly in terms of human history.
This unit explores Solar power as a source of directly useable energy.
This unit is from our archive and is an adapted extract from Earth's physical resources: origin, use and environmental impact (S278) which is no longer taught by The Open University. If you want to study formally with us, you may wish to explore other courses we offer in.
This free course includes adapted extracts from an Open University course which is no longer available to new students. If you found this interesting you could explore more free Environmental Science courses or view the range of currently available OU Environmental Science courses.
Copyright & revisions
Originally published: Wednesday, 20th July 2011
Last updated on: Thursday, 11th October 2012
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